Coiled filter element and method of manufacturing the same

ABSTRACT

An elongated strip of filter material is wound into a coil and consists of two superimposed strip portions connected to each other at their one side and spaced from each other at their opposite side. The strip portions, in consecutive windings of the strip, are spaced from each other at their connected sides and connected at their spaced sides to respectively form first and second parallel adjoining filter pockets of substantially Vshaped cross section, open at the opposite end faces of the coil. Transverse corrugations are provided in the strip portions and afford adjustments in the length of the respective strip portions to the extent such adjustments are necessary during the convoluting of the strip portions into coil shape.

[111 3,759,391 [4 1 Sept. 18

United States Patent [1 1 Dreher I COILED FILTER ELEMENT AND METHOD Chase FOREIGN PATENTS OR APPLICATIONS OF MANUFACTURING THE SAME 755,481 8/1956 Great Britain...................... 210/494 [75] Inventor: Adolf Dreher, Unterhausen,

Germany [73] Assignee: Robert Bosch GmbH, Stuttgart, rim ry amine -56mm N. Zahama Germany 1 Assistant Examiner-F. F. Calvetti Attorney-Michael S. Striker [22] Filed: Oct. 2, 1972 [5 7] ABSTRACT An elongated strip of filter material is wound into a coil 21 Appl. No.: 293,

Related US. Application Data Continuation of Ser. No. 74,605, Sept. 23, 1970, abandoned.

and consists of two superimposed strip portions connected to each other at their one side and spaced from each other at their opposite side. The strip portions, in

[30] Foreign Application Priority Data consecutive windings of the strip, are spaced from each Sept. 26, 1969 Germany..,................

p 19 g 704,8 other at their connected sides and connected at their spaced sides to respectively form first and second parallel adjoining filter pockets of substantially V-shaped cross section, open at the opposite endfaces of the coil. Transverse corrugations are provided in the strip portions and afford adjustments in the length of the respec- 76 9m M74 02 i C St Um 2 1 555 [ll Field of Search............................

tive strip portions to the extent such adjustments are References Cited UNITED STATES PATENTS necessaryduring the con'voluting of the strip portions into coil'shape.

10 Claims, 1 Drawing Figure 3,279,616 10/1966 B0urdale......t..................210/497X COILED FILTER ELEMENT AND METHOD OF MANUFACTURING THE SAME This is a continuation, of application Ser. No. 74,605, filed Sept. 23, 1970, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a coiled filter element, particularly for liquids, and a method of manufacturing the same.

Conventional coiled filter elements in the art are made of an elongated strip of filter material and consist of two superimposed strip portions which, lengthwise, are connected at their one side and open at their opposite side and which, in wound condition, are collectively interconnected at their open sides and spaced at their connected sides so as to respectively define first and second parallel adjoining filter pockets in the coil with the filter-pockets open at the opposite end faces of the coil.

One such known coiled filter element comprises consecutively wound strip portions of a paper filter material and which, in conjunction with a spacer strip arranged at the opposite longitudinal sides of the strip portions, define a substantially V-shaped cross section.

In winding the strip portions to form a coil, a linear differential between the length of the inner strip portion relative to that of the outer strip portion necessarple but effective compensation for the length differential which develops between the inner and outer strip portions when they are wound into the form of a coil.

A further object of the present invention is to provide a method of manufacturing such a coiled filter element according to the invention.

The coiled filter element according to the invention comprises a spirally wound elongated strip of filter material consisting of two superimposed strip portions extending lengthwise of the strip and each having two longitudinally extendingmargins located at opposite lateral sides of the strip. Each of the strip portions is provided with a plurality of at least substantially parallel corrugations extending transversely to the elongation of the strip. First spacing means are interposed between the strip portions and extend along and space apart the margins thereof at one lateral side of the strip, and second spacing means are disposed on and extend along the margins of the strip portions at the other lateral side of the strip for spacing apart the consecutive convolutions of the coiled filter element. During winding of the superposed strip portions the corrugations of the other strip portion flatten as they permit the other strip portions to be sufficiently longitudinally stretched to compensate for the length differential which would otherwise develop between it and the inner strip portion.

ily develops, and it has been found that even by using strip portions made of crepe paper, it is impossible to provide sufficient compensation to maintain the edges of both strip portions in overlapping relationship.

A paper strip folded in itself to V-shaped configuration in order to obtain the inner and outer strip portions, could under these circumstances be wound into a coil only under the application of considerable tensile forces; this, however, would prevent the formation of satisfactory filter pockets in the coil.

Consequently, although the use of such coiled filter elements is-theoretically known, they have not been ac- 2 tually made and used heretofore because of these manufacturing problems. 1

Further known are coiled filter constructions which, in order to overcome the above disadvantages, employ two spirally wound paper strips whose longitudinal margins extending at the axially opposite end faces of the filter element, are alternately connected in permeable and impermeable relationship.

Even though this latter type of filter construction avoids the above-discussed length-differential problem, it has the disadvantage that it requires adhesive seams or connections which are twice as long as those needed in the first mentioned type, which is uneconomical and expensive as regards the costs of manufacturing and of materials, not to mention the greater likelihood of leaks along these longer seams. I

Further known is coiled filter element which, in or er to provide a length compensation ofone stripportion relative to the other, utilizes two filter material strip portions of unequal length. This avoids the abovediscussed problem, but such a construction cannot be economically manufactured.

SUMMARY OF THE INVENTION Object of the present invention is to overcome the above disadvantages and to provide a simple but effectively and economically constructed coiled filter element which is designed in such a way as to afford a simgated spacer strip 4 extends along the margin 1 l at that The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The inventionitself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be bestunderstood from the following-description of specific embodiments when read in com nection with the accompanying drawing. 1

- BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS The filter elementcoil 1, particularly for use with liquids, essentially comprises a crepe paper strip 2 which is folded upon itself in substantially V-shaped configuration to provide the strip portions 2a and 2b which are superimposed 'and longitudinally coextensive. Two spacing strips 3, 4 and adhesive filaments 5, 6, are spirally wound to the shape of the coil 1 together with the strip 2 onto core tube 7. a a a The two strip portions 2a, 2b are provided with a plurality of transverse corrugations 8 which are adjacent one another longitudinally of the strip 2. The folded crepe paper strip 2 can most easily be formed with such corrugations by advancing it through a pair of loosely intermeshing spur gears, not shown, tothereby form the closely arranged, parallel corrugations 8 in the strip sections 2a and 2b. Aside" from their lengthcompensating function, the corrugations also reinforce the paper and consequently improve the pressure resistance of the filter element coil 1.

Provided between the margins 9 and 10 at the open side of the substantially V-shaped paper strip 2, is a first corrugated spacer strip 3, to maintain these margins slightly spaced apart from one another. A similar corruside of the strip portion 2a which faces the interior of the coil 1.

On the same side of the strip portion i l convolutions. provided two adhesive filaments 5 and 6 which extend along the margin 9 and serve to maintain consecutive convolutions of the coil 1 slightly spaced as well as to provide a seal between such consecutive voconvolutions.

In this manner, the coil 1 is provided, when the strip 2 is convoluted, with two spirally intercalated filter pockets 12 and 13 of which pocket 12 is open for entry of fluid at the axial end 14 of the coil while the pocket 13 is open for the same purpose at the other axial end 15 of the coil 1.

If the material of the strip 2 is relatively readily stretchable, either inherently or because of its creping, it may be advantageous not to provide the margins 9 and where the filaments 5 and 6 are located with the grooves or corrugations 8. Instead, these margins 9 and 10 could be flat or almost flat, thus reducing the quantity of adhesive filament required to obtain the desired effects.

The present invention, compared to what is known from the art, requires adhesive seams which are approximately only half as long as known from the art. This is not only reflected in a saving of material, but also permits much more rapid and economic manufacture of the novel filter element and at the same time increases the reliability of operation of the element, the latter factor being aided by the fact that the novel element has a larger active surface area available for filtration purposes. According to another concept of the invention it is also possible to omit one of the spacer strips 3 and 4 Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended withinthe meaning and range of equivalence of the following claims. 1

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A coiled filter element, comprising a coil of an elongated strip of filter material transversely folded upon itself so as to produce superimposed longitudinally coextensive strip portions each having two longitudinally extending margins respectively located at one and at another lateral side of said strip, said strip portions being of one piece with one, another along-said margins of said other lateral side of said strip; a plurality of at least substantially parallel corrugations provided in each of said strip portions and extending traiisversely to the elongation of said strip, the convolutions of said strip defining two spirally convoluted internal filter pockets one of which is open at one axial end of the coil and the other of which is open at the other axial end of the coil, and said corrugations enabling compensation of length variations which occur due to convoluting of said strip in one of said strip portions with reference to the other strip portion with which said one strip portion is of one piece along said margins at said other lateral side; and sealing means sealingly connected consecutive convolutions of said coil in the region of one of said axial ends of the coil, which end lies opposite to said other lateral side of said strip at which said strip portions are of one piece with one another.

2. A filter element as defined in claim 1, and further comprising spacing means extending along said margins in the region of one of said axial ends of the coil.

3. A filter element as defined in claim 2, wherein said spacing means extending along said margins at said other lateral side and spaces said margins apart.

4; A filter element as defined in claim 2, wherein said spacing means comprises a spacing strip having a width substantially smaller than the width of said strip portions and extending along at least substantially the entire length of the latter.

5. A filter element as defined in claim 4, wherein said spacing strip haslongitudinally adjacent transverse corrugations spaced and configurated differently from said corrugations of said strip portions for preventing interengagement therewith.

6. A filter element as defined in claim 1, and further comprising first spacing means extending between the margins of said strip portions at said one lateral side and spacing said margins apart; and second spacing means extending along the margins at said other lateral side and spacing apart consecutive convolutions of the coil.

7. A filter element as defined in claim 1, wherein said corrugations'are spaced at identical distances longitudinally of said strip.

8.'A filter element as defined in claim 1, wherein said corrugations extend over the entire width of said strip portions.

9. A filter element as defined in claim 1, wherein said corrugations extend over only part ofthe width of said strip portions, and wherein said margins of said strip portions are free from said corrugations at least at one of said lateral sides. I I

10. Method of manufacturing a coiled filter element, comprising the steps of forming an elongated strip of filter material transversely folded upon itself so as to produce superimposed longitudinally coextensive strip portions extending lengthwise of said strip and each having two longitudinally extending margins located at opposite lateral sides ofsaidstrip, with the margins at one lateral side of said strip portions being of one piecewith each other; forming a plurality of at least substantially parallel transverse corrugations in each of said strip portions of said elongated strip; providing adhesive means on said strip portions along said margins at the other lateral side of said strip; and convoluting said strip to form a coiled element having a plurality of convolutions forming a pair of spirally convoluted filter pockets one of which is open at one axial end of said coiled element and the other of which is open at the other axial end of said coiled filter element. 

1. A coiled filter element, comprising a coil of an elongated strip of filter material transversely folded upon itself so as to produce superimposed longitudinally coextensive strip portions each having two longitudinally extending margins respectively located at one and at another lateral side of said strip, said strip portions being of one piece with one another along said margins of said other lateral side of said strip; a plurality of at least substantially parallel corrugations provided in each of said strip portions and extending transversely to the elongation of said strip, the convolutions of said strip defining two spirally convoluted internal filter pockets one of which is open at one axial end of the coil and the other of which is open at the other axial end of the coil, and said corrugations enabling compensation of length variations which occur due to convoluting of said strip in one of said strip portions with reference to the other strip portion with which said one strip portion is of one piece along said margins at said other lateral side; and sealing means sealingly connected consecutive convolutions of said coil in the region of one of said axial ends of the coil, which end lies opposite to said other lateral side of said strip at which said strip portions are of one piece with one another.
 2. A filter element as defined in claim 1, and further comprising spacing means extending along said margins in the region of one of said axial ends of the coil.
 3. A filter element as defined in claim 2, wherein said spacing means extending along said margins at said other lateral side and spaces said margins apart.
 4. A filter element as defined in claim 2, wherein said spacing means comprises a spacing strip having a width substantially smaller than the width of said strip portions and extending along at least substantially the entire Length of the latter.
 5. A filter element as defined in claim 4, wherein said spacing strip has longitudinally adjacent transverse corrugations spaced and configurated differently from said corrugations of said strip portions for preventing interengagement therewith.
 6. A filter element as defined in claim 1, and further comprising first spacing means extending between the margins of said strip portions at said one lateral side and spacing said margins apart; and second spacing means extending along the margins at said other lateral side and spacing apart consecutive convolutions of the coil.
 7. A filter element as defined in claim 1, wherein said corrugations are spaced at identical distances longitudinally of said strip.
 8. A filter element as defined in claim 1, wherein said corrugations extend over the entire width of said strip portions.
 9. A filter element as defined in claim 1, wherein said corrugations extend over only part of the width of said strip portions, and wherein said margins of said strip portions are free from said corrugations at least at one of said lateral sides.
 10. Method of manufacturing a coiled filter element, comprising the steps of forming an elongated strip of filter material transversely folded upon itself so as to produce superimposed longitudinally coextensive strip portions extending lengthwise of said strip and each having two longitudinally extending margins located at opposite lateral sides of said strip, with the margins at one lateral side of said strip portions being of one piece with each other; forming a plurality of at least substantially parallel transverse corrugations in each of said strip portions of said elongated strip; providing adhesive means on said strip portions along said margins at the other lateral side of said strip; and convoluting said strip to form a coiled element having a plurality of convolutions forming a pair of spirally convoluted filter pockets one of which is open at one axial end of said coiled element and the other of which is open at the other axial end of said coiled filter element. 